Catheters provide for the diagnosis and treatment of disease without invasive surgery and, accordingly, are widely used for a variety of medical procedures. Unfortunately, the vast majority of catheters available today are manufactured and packaged as entirely disposable, single use devices. While these conventional catheters are undeniably beneficial in shortening hospital stays and in reducing complications associated with surgery, the precision and quality control required to fabricate these instruments makes them expensive to produce. This is particularly true for disposable catheters. Moreover, the use of disposable catheters tends to increase the amount of medical waste generated, to increase the amount of packaging waste generated and eliminate the ability to adapt the configuration of the catheter to specific operating conditions.
These and other limitations associated with the use of entirely disposable catheters are particularly well illustrated by catheters used for the treatment of vascular diseases. Over the last decade a medical procedure known as angioplasty has become widely accepted as a safe and effective method for opening stenoses throughout the vascular system and particularly for opening stenoses in the coronary arteries. The most common form of angioplasty practiced to date is known as percutaneous transluminal coronary angioplasty (PTCA).
In virtually all forms of PTCA, a dilatation catheter having an inflatable balloon at its distal end is guided into a patient's artery and maneuvered within the artery until the balloon is positioned across the narrowing stenosis responsible for inadequate blood flow to the heart. Generally, a thin guide wire is used to maneuver and direct the catheter into position. The balloon is then inflated for a brief period, usually for no more than a few minutes, in order to displace the plaque or other obstruction causing narrowing in the artery. The deflated catheter is withdrawn when the stenosis has been opened and blood is once again flowing adequately. Thus, in contrast to the serious risks and complications previously associated with open-heart surgery, PTCA can be utilized to open blocked coronary arteries using only a small vascular incision through which the dilatation catheter is inserted and operated.
Several different types of entirely disposable dilatation catheters are currently in use and may be generally classified based on their interaction with the guide wire. One common dilatation catheter design is known as the "fixed-wire" or integrated "balloon-on-awire" dilatation catheter. In general, these single-lumen catheters utilize a relatively small diameter guide wire positioned within the inflation lumen and fixed to the distal end of the dilatation balloon. This design produces a low-profile assembly which is able to cross severely narrowed lesions and to navigate tortuous vascular pathways. More recent balloon-on-a-wire designs allow the catheter to be removed while leaving the guide wire in place across the stenosis.
Another common type of dilatation catheter is known as an "over-the-wire" balloon catheter. This dual-lumen device typically utilizes a relatively large lumen for passage of a guide wire and injection of angiographic visualization dye to assist in the placement of the expansible balloon. A second parallel lumen is provided for inflation and deflation of the balloon.
More recently "rapid exchange" catheters have been developed to allow the quick removal of the catheter from the patient while leaving the guide wire in place. One such rapid exchange system, utilizes a conventional inflation lumen and a relatively short guiding or through lumen slidably received over a guide wire at the distal end of the catheter. The distal portion is permanently fused to the catheter body tube which is formed of a flexible material that allows the catheter to be pushed through curved vascular pathways.
Other "rapid exchange" catheter designs use a dedicated guide wire lumen provided with a longitudinal split seam. These designs enable the operating physician to remove the catheter by simply grasping the catheter's proximal end and pulling the catheter tube off of the guide wire. Still other designs use a blade to split the catheter upon its removal from the patient. For example a sharpened blade may be mounted within the central bore of a modified Y-connector to slit the catheter and separate it from the guide wire as it is extracted.
While these disposable catheter designs have proven effective under various conditions, the lack of reusability drives up the costs associated with their use while limiting the ability of the surgeon to adapt to changing or unexpected situations. For example, when a standard over-the-wire catheter configuration is used in an angioplasty procedure, several catheter components that do not come in contact with patient and are never subjected to physical stress are discarded. Similarly, when more than one size of expansible balloon is required in an operation the entire catheter assembly must be discarded and substituted with a catheter having the desired balloon size. The disposal of these technically advanced, precision manufactured instruments which are otherwise suitable for repeat use, reduces the efficiency of the entire procedure.
In an early effort to circumvent the disadvantages associated with the use of completely disposable catheters, it was suggested that they be resterilized and reused. However, such operations have proven to be unworkable in practice. Most of the currently available catheters are fabricated as substantially integral devices having many components joined or fused using permanent connections. As such they are not readily disassembled for the purpose of resterilization. Moreover, in order to reuse the catheter several delicate pieces of the assembly must be repeatedly subjected to harsh sterilization conditions, which may increase the possibility of material deterioration and subsequent malfunction.
This is particularly true of the thin walled, expansible dilatation balloon of the catheter. The balloon must exhibit a consistent inflation profile upon the application of several atmospheres of pressure. When subjected to repeated sterilization procedures the balloon may become distorted and fail to fold or expand properly. Further, any sterilization induced hysteresis may decalibrate the balloon sizing accuracy for future uses.
Similarly, the configuration of the catheter itself may preclude the efficient resterilization of the apparatus. Many standard catheters incorporate a closed system inflation lumen that must be entirely purged prior to sterilization to ensure the effectiveness of the procedure. Complete purging of the system is labor intensive, time consuming and expensive after use, if possible at all. Thus, the significant costs involved in resterilization may outweigh the costs of simply replacing the device.
Accordingly, it is an object of the present invention to provide catheters which incorporate resterilizable and reusable components.
It is another object of the present invention to provide dilatation catheters which allow for the rapid and uncomplicated substitution of components and for modified catheter configurations.
It is yet another object of the present invention to provide dilatation catheters which require less storage space than disposable catheters while simultaneously reducing the amount of packaging necessary to maintain their sterility prior to use.